FTdx101D/MP Spice Analysis and ttbf Mode Enable
This section was started to provide a detailed analsysis of the new Yaesu FTdx101 series (D/MP) radio's "audio" ckts using Spice to ensure that the
audio circuits were designed to cover the needed bandwidth. Then, the ttbf mode was found after an FW upate was released. Finally, two examples of
actual user captured frequency spectrum via SpectraPlus is presented.

Link to the Yaesu web site for the latest FW release: click
here then click on the "FILES" tab.
Latest FW release: "202003" date 3/16/20

Up to Mar 16, 2020, Yaesu has pulled a fast one on the buyers of the new FTdx101D and FTdx101MP radios. It appears that
they are playing games by initially "giving" the user only 3KHZ RECEIVE bandwidth and then, probably after many
buyer complaints, releasing a FW update that now gives 4Khz RECEIVE BW but NO "ttbf" SSB TX mode that is present
on the FTdx9000, FTdx5000, FTdx3000, FTdx1200 and FT2000 radios. And MANY are very angry and disappointed. But that's
Yaesu!!

I believe Yaesu is still designing the radio as it sells them! And since this is a new technology field for Yaesu -
SDR, I'm not sure that they can release a future FW update that will give the fabled "ttbf" mode on SSB TX. The
FW release at the end of June shows there there is still pressure to continue the "ttbf" tradition in their radios even
in the new SDR field.

One customer called Yaseu and asked about the "ttbf" mode: he was told that at THIS time, the function is not
available; however his call was logged and forward to the engineering dept. So there may be hope . .

Personally, if the ttbf mode isn't added, I wouldn't buy the radio! The 101D price tag is $3300 and 101MP is
$4400. The 101D requires an external 13.8V DC power supply and a speaker. The 101MP comes
with a power supply (FPS-101) which has a speaker in the external cabinet. It should be the same for the 101D. In my
opinion this SDR Yaesu radio is in the beta-testing stage!! They have far more issues with new releases than all
other companies combined.

Yaesu owners will remember the "PEP" . . Performance Enhancement Program from Yaesu where they literally replaced
the "insides" of FTdx9000 and other radios and installed FW that actually did something! My FT2000D received all new FW
for the "operating" and "features" updates where the Noise Blanker, for example, actually started to work!

Personally, I'd get a used FTdx5000MP and be very happy! However, as of Mar 16, 2020, Yaesu released a FW update:
202003 and you can now attain the fabled 'ttbf' mode for SSB TX. Details at the bottom of this section.

---- click on any picture to enlarge ----

Here's the FTdx101D mic preamp schematic:

After capturing the above schematic into 5Spice, it appears as shown:

As you can see, the preamp's audio BW is certainly quite good - 16hz to 5.7Khz - without the need to
REPLACE any component! That's a first for Yaesu. Normally, they usually RESTRICT the audio peramp BW resulting in ckt component
modifications to give sufficient audio bw. It's about time they got it right!

However, this excellent response is degraded in the following stages BEHIND the mic preamp. I personally
have observed cutoff below 100hz and above 2.5Khz in the final RF output so this audio is not being utilized. That is
unfortunate.

You see that there's an analog mux that selects the signal into a gain opamp, then through R-C filter which attenuates the signal by
over -100dB and then through a "peaking" opamp filter which peaks the signal.

The follow-on ckt consists of what is called the "Buffer-Filter Ckt" and the schematic show it captured into 5Spice for analysis.
The ckt appears to be "strange" in that there is a low-pass-attenuator consisting of resistor/capacitors around Q9014. This ckt attenuates
the preamp signal by over 100dB. Then Q9033 opamp "peaks" the response. This is strange indeed!!!

The 5Spice analysis shows the conditioning that occurs to the excellent mic preamp signal to deteriorate it as shown. As you see, the
Lo cut = 16hz, Hi cut= 5.5Khz with a PEAK response point at 3.5Khz @ 7dB! Certainly not standard processing IMO.

---- FTdx101D/MP 'ttbf' mode enable ----

Received email from Damon, KJ7Eregarding the latest FW update: 202003 of 3/16/20. Here's what he wrote:
Been a long time, lots to talk about, but I picked up an FTDX101MP a few months ago and just figured out how to enable the TTBF for extended
TX bandwidth. With the latest 202003 firmware update package you can enable the TTBF TX BPF option. Same as the
FTDX5000, power on and press DNR+DNF buttons on the main RX side (lower set).

Did a real quick sweep between the two settings this morning, didnít plot it but here are the results;

[Also received an email from Terry W6RU and he confirms the addition of the 'ttbf' mode by following
the above instructions. Charles, W4CO has also reported that performing the FW update does indeed give
the ttbf mode on his FTdx101MP.]

The left and right charts show the FTdx101 and FT2000D @ 100W frequency response respectively. My FT2000D was swept using a Sony
MZ-R55 with a pre-recorded "white", "pink" and "tone" sources w/o any EQ and then with EQ. I picked the "Tone" curve b/c it
matches the method used by KJ7E.

Look at the shape of each curve: the FTdx101 output exhibits "pwr-sag" at two (2) places: below 150hz and above 3.2Khz. I've
drawn two (2) 'correction' lines that match the FT2000D response.

Comparing the output levels are various frequencies shows a rolloff at low frequencies (below 120hz) and high freguenices (above
3.4Khz). As you read in the SPICE section above, the Mic Preamp does NOT restrict the signal's BW. However, there is some
"strange" equalization in the BUFFER/FILTER ckt that is hard to explain why it would be needed??

---- FTdx101D/MP 'EQ' Solutions: KJ7E ----
The chart shows a SSB TX spectrum from KJ7E's FTdx101MP from 50hz to 4Khz "FLAT" response. This is the "actual"
response recorded by K6JRF using SpectraPlus on my FT2000D that has been EQ flat from 50hz to 4Khz. Compare the
ttbf vs 50-3050 mode. The Hi Freq response is quite good
in that it extends to 3.8Khz, certainly adequate, but not excessive, for an ESSB transmission.

Here is the plot that I captured today (4/5/20) on 40mtrs. Damon, KJ7E operates in the "50-3050" mode, not 'ttbf'.
Note that the EQ has been expanded and flattened from 110hz to 3.2Khz. Excellent sounding and extremely clean!
Also note that he has +16dB of GAIN at 3.2Khz and 3.7Khz to effect decent HI Freq response. That shows how much
loss there is in the SSB TX path in the radio above 3.2Khz! That's NOT RIGHT!

---- FTdx101D/MP 'EQ' Solutions: WA6OT ----
For contrast, here's the SpectraPlus chart of WA6OT with his FTdx101D in the ttbf mode. Note
the excellent LO FREQ and HI FREQ response from the radio with external EQ applied. This is the latest SprectraPlus sweep as
of 4/11/20.

To attain the balanced response, the settings for the Behringher Ultra-Curve 2496 are shown in the chart. The radio's rolloff
causes the high "GAIN" settings needed to overcome this loss. But it appears that decent ESSB SSB TX can be had with the proper
EQ - but a LOT of IT is required! Of course, it would be much better if the radio had a flatter response. Maybe with hardware changes,
it could be made to be???

I understand that the SSB TX signal is directly created by a D/A converter. It's amplified to the needed power level and
outputted. There must be some non-linearities in the drive signal (as we saw in the Buf/Filter ckt) or in the output drive
to the final RF TX amplifier. The chain needs to be investigated!